In accordance with current standards, in mobile communications technology for example, reflectors are used for mobile communications base station antennas, the rear side of which reflectors opposite the radiator side is formed in a manner similar to a housing. For example, cabling, phase shifters, adjustment devices for phase shifters, filter assemblies etc. can be accommodated in this space. In this case, the reflector can be provided with side-wall webs, which become fixing flanges which terminate parallel to the reflector plane and to which a reflector cover can then be screwed, for example.
In addition, for mobile communications antennas that meet the packing density of today, active assemblies such as a radio or a remote radio head (RRH) are often also accommodated on the rear side of the reflector. Radios of this kind can simultaneously also function as the housing cover by being correspondingly screwed onto the reflector.
It is therefore invariably necessary to fix the relevant parts to one another using a plurality of screws.
According to a known standard, for example, on the rear side of the reflector on said fixing flanges, a plurality of spaced-apart press nuts can accordingly be press-fitted into holes in the reflector fixing flange in order to create here a pre-fitting arrangement for the subsequent mounting. A cover in which holes are also made can then be placed on the fixing flange. These holes are aligned with the holes in said press nuts. Internal threads are formed in the press nuts themselves, such that suitable screws for fixing the cover can be screwed in from the opposite side.
In all these cases, however, it has been found that above all the press-fitting of said press nuts or the press-fitting of said press-fit bushes can cause very small inclined angles, with the result that there are no uniquely reproduced contact points between the reflector, the cover and/or the housing e.g. of an active component. Contact points that cannot be uniquely reproduced, however, invariably lead to altered conditions, which in particular in HF engineering can produce unwanted intermodulations.
The above-mentioned tolerance errors can arise not only in the vertical direction but also in the horizontal direction with respect to the components to be fastened to one another in a substantially planar manner. These tolerance errors are generally unacceptable or cannot be overcome.
Finally, when the individual assemblies are joined onto one another and screwed together, surface damage can also be caused to the electrically conductive coatings or to the metal, which damage likewise again results in modified contact conditions. In all these cases, the manufacturing process means that there is only very poor control of the contact pressure, again because of different surface areas (diameters of the contact portions).
Nevertheless, the rear reflector space comprising the assemblies and components accommodated therein need to be shielded by placing on an electrically conductive cover. In particular, it is essential to shield the radio from other vital antenna components.
Thus, by screwing together the corresponding shielding parts, shielding against high-frequency interfering radiation in particular is also intended to be achieved, such that no electromagnetic radiation can escape to the outside or, vice versa, no electromagnetic radiation can enter the shielded space from the outside. Shielding against high-frequency radiation is generally of great importance for all aspects of communications technology, including mobile communications.
As well as the infiltration of undesired signal components, undesired intermodulation products may also occur.
The most frequent cause of electromagnetic interfering radiation is the deficient design of the connection between housing walls and corresponding cover parts. Small gaps, which act like slot antennae, can greatly reduce the shielding attenuation. These gaps result from poor contacts, tolerances and/or from irregularities or unevenness between the housing walls or cover surfaces that are placed on one another at corresponding contact portions.
WO 2013/033894 A1 discloses an antenna arrangement that comprises an antenna/signal processing unit having a first groove arrangement, and an antenna portion having a second groove arrangement, which processing unit and antenna portion can be inserted into one another using a gasket body.
Furthermore, WO 2013/096880 A1 discloses that capacitive couplings can be provided between different modules, for example between a main module and a sub-module.
In contrast, the object of the present invention is that of providing a capacitively shielded housing, in particular a capacitively shielded component housing, for an antenna device, for example a mobile communications antenna.
The problem is solved according to the invention in accordance with the features specified in claim 1. Advantageous configurations of the invention are described in the dependent claims.
If, for example, corresponding antenna components such as cables, phase shifters, adjustment devices and filter assemblies, etc. are accommodated on a housing or reflector housing, on the side of an antenna arrangement or mobile communications antenna device that is to the rear with respect to the radiators, and this housing space is shielded from a radio or remote radio head to be placed thereon, or in general shielded from other HF electronics, by placing on a shielding plate, within the context of the invention it is then possible to avoid having to rigidly mount said shielding plate on the corresponding reflector housing using a plurality of screws as is otherwise conventional.
In addition, within the context of the invention, undefined contact points and contact conditions, such as occur or can occur in particular in a fixing method using a plurality of screws, are avoided.
According to the invention, for this purpose it is provided, in principle, that the housing space to be shielded should comprise housing contact regions or housing flanges, on which corresponding contact regions or flanges of the shielding plate rest.
In this case it is provided, according to the invention, that the housing or housing parts that are each conductive or are coated with an electrically conductive surface, on the one hand, and the shielding plate on the other hand, are not galvanically interconnected in the contact region thereof, but rather are galvanically isolated from one another with the interposition of an insulation layer or insulation film, with the result that a capacitive coupling between the housing, i.e. in particular the reflector component housing, and the shielding plate or shielding cover is produced in this case in the application or contact region of the corresponding application and/or contact portions. Capacitive shielding of this kind has significant advantages compared with galvanic contacting of the corresponding components e.g. by means of the above-mentioned use of screws. The invention prevents undefined contacting conditions and thus above all counteracts the risk of intermodulations.
According to the invention, the corresponding contact surfaces are not perpendicular to the mounting direction, and are therefore in general not perpendicular to the orientation of the opening plane of the housing or reflector housing but instead extend in parallel therewith. In other words, the corresponding capacitively coupled application and/or contact regions or flange regions between the reflector housing on the one hand and a shielding covering and/or a shielding plate on the other hand are oriented parallel to the mounting direction and thus parallel to the central axis and/or mounting direction.
This results in the further advantage, which can be achieved within the context of the invention, that the corresponding application portions or contact portions, on which the capacitive coupling between the reflector housing and the shielding plate is formed, do not result in an increase in the required installation space in the attachment direction, but rather that the parts can be inserted into one another in the mounting direction and therefore it is not necessary to increase the installation space in the mounting direction in order to implement the invention.
However, it is also possible, within the context of the invention, that the corresponding capacitively coupled application or contact portions between the reflector housing and the shielding plate are not necessarily oriented parallel to the mounting direction, and thus necessarily parallel to a central axis extending through the reflector housing, but rather extend, for example, obliquely towards the mounting direction or the central axis and are designed and/or adjusted accordingly. The contact surfaces that bring about the capacitive coupling therefore do not necessarily have to be oriented at an angle of 0° relative to a surface extending perpendicularly to the mounting direction of the central axis (and thus parallel to the central axis or mounting direction), but can instead extend at an angle of between 0°≤α<90°. If the angle were α=90°, the two contact surfaces would extend perpendicularly to the mounting direction or to the central axis, i.e. would come to rest on one another, as a result of which the height of the overall structure would increase, which is to be avoided according to the invention.
The angle α can preferably assume values that deviate from 90° as significantly as possible, in order to permit the contact surfaces to at least extend obliquely towards the mounting direction or the central axis.
Finally, within the context of an advantageous embodiment, it is also provided for corresponding electrically non-conductive (dielectric) retaining elements to be provided at the corresponding mounting points, preferably on at least one of the two capacitive application portions that are to be brought into contact. According to the invention, for this purpose corresponding retaining nipples can be clamped (preferably without the use of tools) in corresponding holes, for example in the reflector housing, at a distance from the mounting plate to be mounted, onto which nipples the contact surfaces to be shielded, for example of the shielding plate, can then be pushed in order to be retained in a predefined non-positively loaded contact position that is as parallel as possible, relative to the corresponding contact portion of the reflector housing, while forming the capacitive coupling.
Finally, a further force-loading and/or orientation device is preferably formed, preferably on the shielding plate, which device makes it possible for the contact surfaces provided on the shielding plate for the capacitive coupling not to come to rest at an angle to the corresponding contact surface, for example of a housing and in particular of a reflector housing, but in fact rather to come to rest so as to be oriented in a manner as parallel as possible, i.e. exactly parallel. This can be ensured by means of an appropriately pre-impressed deformation on the shielding plate. This can be achieved, for example, by the actual shielding plate portion transitioning via an impression that has, for example, an S-shaped cross section, into the adjacent preferably plane-parallel contact portion (that comes to rest parallel to the contact surface of the component and/or reflector housing in order to produce a capacitive coupling). This S-shaped pre-impression or equivalent measures make it possible for the contact surface of the shielding plate to adapt to the corresponding orientation and position of the contact surface of the component and/or reflector housing. In this case, the S-shaped deformation can, in some circumstances, even produce some force-loading towards the contact surface of the component and/or reflector housing if the overall width of the shielding plate together with the contact surfaces is at least slightly wider than the opening width of the component and/or reflector housing. Moreover, this design makes it possible for the contact surfaces of the shielding covering or of the shielding plate to accordingly orient themselves in an optimal manner relative to the contact surfaces of the component and/or reflector housing.
In addition and alternatively, a corresponding shielding plate can also be divided in two, for example, the two shielding plate portions or halves overlapping at least in part, and forming a capacitive coupling. This makes it possible, for example, to adjust the width of the shielding plate to the housing opening to be shielded, thus ensuring that the contact portions can precisely occupy the exact position in which they bring about the capacitive coupling while forming a uniform spacing by interposing a dielectric layer.